The invention relates to a wheel drive for mobile vehicles preferably omnibuses and particularly low platform buses.
By their nature wheel drives stand out by the fact that they can be installed in the vehicle so as to occupy little space in axial direction in order, for example, to obtain the largest possible gear width in a bus. For this purpose, wheel drives are configured so that the main mover part can be lodged within a rim of the wheel. Wheel drives can be actuated either via a common drive motor, which communicates with the wheel drive, via a torque divider or via a drive motor directly connected with the wheel drive.
EP 0 523 472 B1 discloses a gantry axle for a bus where, in order to obtain a gantry clearance as large as possible, a drive motor actuates a gearwheel, via a torque divider which, on one side, communicates with an outer central wheel and, on the other, drives a gearwheel which, as intermediate wheel, actuates one other gearwheel which, in turn, is connected with the outer central wheel, the outer central wheel forming the output. By the driven gearwheel being in intermeshing connection directly with the outer central wheel, a very large gantry clearance is obtained, but the tooth loads on the driven gearwheels are very heavy, since the driven gearwheel has only two opposite meshings of teeth through which the torque of the driven gearwheel can be generated. Thereby the driven gearwheel, the same as the other gearwheels and the outer central wheel, must be designed with a diameter such that they can be situated only outside the rim.
The invention is based on the problem of providing a wheel drive by which a largest possible gantry clearance can be implemented and which can be so compactly designed that at least the reduction gear can be situated within the diameter of the rim and the largest possible gear width is obtained in the vehicle by the compact axial design of the wheel drive.
According to the invention, the wheel drive consists of a reduction gear in which a driven gearwheel is in intermeshing connection, on one side, with an outer central wheel and, on the other side, with at least two gearwheels which are in operative connection with the outer central wheel. The teeth meshings of the outer central wheel with the driven gearwheel and the teeth meshings of the other gearwheels with the driven gearwheel are disposed so that the lines of action of the radial forces generated by the teeth meshings with the driven gearwheel strike on the axis of rotation of the driven gearwheel. By the driven gearwheel, having at least three teeth meshings by which the torque, can divide itself, it is possible to design the driven gearwheel, the other gearwheels and the outer central wheel compactly enough so that the reduction gear can be situated within the diameter of the rim. By the lines of action of the radial forces striking on the axle of rotation of the driven gearwheel, it is possible to omit a bearing of large dimensions of the driven gearwheel, since the driven gearwheel can be supported either floatingly or via a small bearing. Due to the floating bearing of the driven gearwheel and at least three teeth meshings, the action lines of which strike on the axis of rotation of the driven gearwheel, the driven gearwheel can adjust under torque load so as uniformly carry all teeth meshings whereby the reduction gear can be more compactly designed. The gearwheels which are in intermeshing connection with the driven gearwheel are preferably disposed so that the angle resulting from the connection of the central points of rotation of the two gearwheels with the central point of rotation of the driven gearwheel is less than 120xc2x0. By the angle being designed of less than 120xc2x0, it is not possible to uniformly distribute the torque load onto the three teeth meshings but onto the teeth meshing of the driven gearwheel with the outer central wheel, since here the curvature ratios are more favorable for loading with a great torque than the teeth meshing of the driven gearwheel with the other gearwheels. Hereby the other gearwheels can be designed more compact. The driven gearwheel is preferably actuated via an electric drive motor. But the driving can also result via an input shaft from a torque divider. The outer central wheel which forms the output can be connected directly with the output of the wheel drive or drive an inner central wheel of a planet step whereby the total ratio is increased and the drive motor can be designed more compact. By it being possible very compactly to design the reduction gear as consequence of several teeth engagements on the driven gearwheel and obtaining a very large gantry clearance, it is possible to situate within the rim diameter a brake which is connected with the output of the wheel drive and place one part of the actuation device of the brake within the rim diameter so as to create a wheel drive more compact in axial direction. By virtue of the arrangement of the reduction gear of the brake, the same as of the actuation device thereof, and of one part of the drive motor within the rim wherein the mass center of gravity is located on the inner side of the wheel, an improvement of the suspension properties is obtained.